I'd much rather see enemies get buffed than players get nerfed. Increasing the challenge is always better than nerfing the tools that people have fun with and are used to. I *like* feeling like a god when I press thunderstorm and watch everyone get zapped. It's a really cool animation and I feel powerful. I don't want that to trivialize every fight, though, which it currently does. I want enemies to have powerful tools to combat me instead of just being lambs to the slaughter.
I think it would make sense to have enemies that are immune to hard CC, but could still suffer soft-CC sorts of debuffs like chilled, shocked and slowed. It might benefit the gameplay to add a few more debuffs that replace hard CC effects for enemies immune to them. IE: when you use battle stomp on an enemy immune to knockdown, instead of just saying 'immune' and doing nothing, they can be affected by an 'unsteady' debuff that slows their movement and reduces their accuracy slightly. Just an example ofc.
Hard CC is generally just not a fun mechanic in any game. The general rule, I think, is for any hard CC to have a short duration, not be spammable, and should hard to chain together. Divinity has most on short durations, but they're very much spammable and easy to chain together. I'd love to see 'perserverance' become a more powerful stat and I'd like to see enemies get significantly higher levels of it than they currently do. At a certain level of perserverance I'd like to see it offer one turn of immunity to hard CC upon proccing. IE: get up from knock down, you are now affected by the 'perservering' buff for one turn which makes you immune to all hard CC. Chain stunning is now gone, fights now become more challenging and feel less like one-sided snowballs.